Addiction and neural ageing
Addiction and neural ageing

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Glossary for SD805_2
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An antagonist to opioids. It can cause distress and some signs of withdrawal if injected by heroin users, a so-called naloxone challenge.


An opioid (opiate) drug, e.g. morphine or heroin.

natural selection

Driving force of evolution as described by Darwin. In the competition for resources between individuals in an environment that cannot support all of a population, a natural process of ‘selection’ occurs in which individuals with the most adaptive characteristics are more likely to survive and reproduce.

nature–nurture debate

This refers to debates about the relative contributions of genetic inheritance (nature) and environmental influences (nurture) to the physical/ behavioural characteristics of an organism or species.

negative cognitive set

Tendency to construe the world in negative terms; characteristic of a depressed mood.

negative feedback

(in cell metabolism) Also called end-product inhibition. It is the mechanism by which a metabolic pathway is regulated: when the product of the pathway exceeds a critical concentration, it ‘switches off’ an enzyme early in the pathway, thereby preventing further synthesis of the regulatory end-product.

negative feedback system

A system in which a displacement of a variable from a state causes corrective action such as to return the variable to that state.

negative reinforcement

nerve cell

Another name for a neuron.

nervous system

The collection of all of the neurons of the body, in brain, spinal cord and periphery.

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